Scavenger - An augmented reality scavenger hunt for cash prizes
A.I. Experiments by Google - Explore machine learning by playing w/ pics, music, and more
Gift Hunt for WordPress - Online treasure hunt on your WordPress site
Swift Playgrounds - Learn serious code on your iPad in a seriously fun way
Play Munzee - Similiar to Geocaching but requires players scan a QR Codes instead to validate find.
Talk to Books by Google - Browse passages from books using experimental AI